Circuit and operating method for integrated interface of PDA and wireless communication system

ABSTRACT

A circuit for an integrated interface of a PDA and a wireless communication system is suitable for integrating the PDA and the wireless communication system. The circuit includes a first serial port has two terminals, in which one of the two terminals is electrically connected to the PDA, and another one of the two terminals is electrically connected to the wireless communication system. The first serial port is used to bi-directionally transmit a control signal between the PDA and the wireless communication system. A second serial port has two terminals, in which one of the two terminals is electrically connected to the PDA, and another one of the two terminals is electrically connected to the wireless communication system. The second serial port is used to bi-directionally transmit data between the PDA and the wireless communication system.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of a prior application Ser. No.10/249,403, filed Apr. 7, 2003. The prior application Ser. No.10/249,403 claims the priority benefit of Taiwan application serial no.91118369, filed on Aug. 15, 2002.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention generally relates to a circuit and operatingmethod for an integrated interface of a PDA and a wireless communicationsystem, and more particularly, to a circuit, operating method forexecuting turn-on-device, power-saving, power-shortage determining, andpower-charging for the integrated interface of a PDA and a wirelesscommunication system.

2. Description of Related Art

In line with personal computer capability enhancement, the demands ofportable computers increase accordingly and their functions are gettingmore and more mature. In the beginning, portable computer meant alighter weight desktop computer that had to use household power supply.However, along with the development of LCD and the long-term battery,the notebook started to be accepted and used widely. The weight of ageneral notebook is about 2.5 kg to 3.5 kg. Therefore, the notebookindeed provides a perfect portability while keeping the completefunctionality of a personal computer.

Since the notebook has acquired excellent performance in the market,many people have aggressively dedicated themselves to the development ofa smaller computer. However, due to the limitation of display size andsuitable input equipment, the development of the smaller computer hadlimited improvement. Nevertheless, finally there has been one smallercomputer to breakthrough the difficulties mentioned above and be wellaccepted in the market. This is a computer that uses few buttons and atouch screen as input equipment, generally called the Personal DigitalAssistant (PDA).

With PDA's high portability, plus the Optical Character Recognition(OCR) software, there is no much difference between a PDA and a generalnotebook in the convenience level of data input anymore. Therefore, thePDA is getting more and more popular in the market. The most commonpurpose of the general PDA is to provide the related information fordaily living, such as calendar, railroad/bus time table, telephonenumbers, and even domestic maps, etc. The general reason why a user usesa PDA is for its excellent portability, with which a user can get theinformation mentioned above to use a telephone at any time, any place.In order to contact with others at any time and any place, or to acquirethe most updated and suitable information, a different sort of thewireless communication systems such as the Global System for Mobile(GSM) system or the General Packet Radio Service (GPRS) system are usedto communicate with others, or through these wireless communicationsystems connecting to the Internet to acquire the most updatedinformation. Either one of the above is a wonderful option.

However, PDA and all other wireless communication systems are soldindependently in the current market. Therefore, besides purchasing a PDAand wireless communication systems, in order to connect to the Internetand acquire information easily, it is also necessary to purchase anappropriate network interface or use a more expensive infraredcommunication device to have mutual information exchange between a PDAand a wireless communication system. Therefore, users not only have toconsider the compatibility between different products when they arepurchased, but also have to carry all kinds of equipment for providinginterfaces, which is really troublesome.

SUMMARY OF THE INVENTION

The present invention provides a circuit and operating method for anintegrated interface of a PDA (Personal Digital Assistant) and awireless communication system. The interface between the PDA and thewireless communication system is provided to integrate the PDA and thewireless communication system, and to further enhance the wholeutilization between the PDA and the wireless communication system.

The present invention provides a circuit and operating method forintegrated interface of PDA and wireless communication system. It issuitable for integrating the PDA and the wireless communication system.The circuit includes two serial ports, the serial ports are electricallyconnected between the PDA and the wireless communication system, and oneof the two ports is used to transmit a control signal, and another oneof the two ports is used to transmit a data signal.

In a preferred embodiment of the present invention, the circuit providedby the present invention further comprises a power system, wherein thepower system provides power to the PDA and the wireless communicationsystem, and also provides a power-shortage signal to the PDA and thewireless communication system when power is insufficient. In anotherpreferred embodiment of the present invention, the power systemdetermines a method for supplying power to a PDA according to an idlesignal received from the PDA. Moreover, in another embodiment of thepresent invention, the power system provides a charging signal to thewireless communication system when it is charged from outside, and thewireless communication system determines the charging mode according tothe charging signal and the power system potential.

The present invention further provides an operating method for anintegrated interface of a PDA and wireless communication system. Theinterface used by the operating method comprises aPDA-turn-on-wireless-communication-system signal line, aPDA-reset-wireless-communication-system signal line, a PDA-state signalline, wireless-communication-system-state/wake-up-PDA signal line andtwo serial ports. Wherein, one of the two ports located between the PDAand the wireless communication system is used to transmit the controlsignal and the status data of the wireless communication system statesuch as the antenna intensity and the battery capacity by using themulti-channel method, and another one of the two ports is used totransmit a digital data signal.

In an embodiment of the present invention, the following turn-on-devicemethod is further used by the operating method according to the presentinvention in the first time PDA power-on: turning on the PDA first, andfurther checking the status of the wireless communication system. If thestatus of the wireless communication system observed is turn-on duringthe checking process, the wireless communication system is reset via thePDA-reset-wireless-communication-system signal line; otherwise, if thestatus of the wireless communication system is turn-off, the wirelesscommunication system is turned on and reset via thePDA-turn-on-wireless-communication-system signal line. After performingthe reset operation of the wireless communication system mentionedabove, the status of the wireless communication system is furtherchecked after waiting for a certain period of time. If the status of thewireless communication system observed is normal in the present time'swireless communication system status checking, the first timeturn-on-device is completed; otherwise, if the status of the wirelesscommunication system observed is abnormal, the error message isdisplayed to notify the external that power on of the wirelesscommunication system turn-on-device has failed.

In another preferred embodiment, the operating method according to thepresent invention further comprises a set of power management system.This comprises a power-saving method, a power-shortage determiningmethod, and a battery charging method. On the power-saving aspect, thepreferred embodiment of the present invention transmits a wirelesscommunication system state signal to the PDA when the wirelesscommunication system starts to operate from a standby state. Meanwhile,if the PDA is currently used, the normal procedure is processedaccordingly. If the PDA is in a sleep state, the PDA is wakened by thesubsequent wake-up-PDA signal. However, the input source of the audioelement in the PDA is switched to the wireless communication systemunder both states mentioned above to facilitate the usage of thewireless communication system. When the wireless communication systemoperates continuously and the PDA does not have any operation for acertain period of time, the PDA is switched to the sleep state.

Moreover, in the power-shortage determining method used by a preferredembodiment of the present invention, the power potential is divided intothree different levels from high to low. For convenience of explanation,the potential levels from high to low are herein called the firstpotential, the second potential and the third potential, respectively.The power-shortage determining method used by the preferred embodimentof the present invention issues a power-shortage signal when the powerpotential starts to be lower than the second potential, and continuouslyissues the power-shortage signal until the power potential is greaterthan or equal to the first potential. Furthermore, if the powerpotential is in between the first potential and the second potential andthere is no power-shortage signal, the system is operated normally.Finally, if the power potential is lower than the third potential, it isfully discharged. Moreover, in a preferred embodiment of the presentinvention, for example, the first potential mentioned above is about 3.6V, the second potential is about 3.5 V, and the third potential is about3.2 V.

The battery charging method used by another preferred embodiment of thepresent invention is suitable for charging the device that uses abattery as power and is charged via an external charging cable. Thedevice further has an external charging circuit for charging a battery,and the wireless communication system has an internal charging circuitfor charging a battery, too. The battery charging method performs asmall-current charging via the external charging circuit mentioned aboveby using the external charging cable when the battery is empty, andtries to turn on the wireless communication system during the periodwhen performing the small-current charging. After the wirelesscommunication system is successfully turned on, when the batterypotential achieves a first predetermined value, the internal chargingcircuit is turned on to perform charging. Furthermore, the battery canissue a charging signal to the wireless communication system when theexternal charging cable mentioned above connects to it, so that thewireless communication system can recognize the current charging status.

In a preferred embodiment of the present invention, the charging methodis switched to the constant voltage charging when the battery potentialachieves a second predetermined value that is higher than the firstpredetermined value mentioned above. When the battery potential falls inbetween the first predetermined value and the second predeterminedvalue, the charging process can be further divided into multiplecharging segments. These charging segments are distinguished from eachother by using the battery potential and use charging speeds withdifferent current values respectively.

The present invention further provides an operating method for anintegrated interface of a PDA and a wireless communication system,suitable for integrating the PDA and the wireless communication system.The operating method comprises using at least one serial port totransmit a control signal and data between the PDA and the wirelesscommunication system. In addition, when the PDA is turned on, the PDA isturned on, and the wireless communication system is turned on by thePDA.

In summary, the circuit and operating method for the integratedinterface of a PDA and wireless communication system integrates a PDAand wireless communication system by using two serial ports, and furtherdefines an integrated set of operating methods, so that the PDA and thewireless communication system can easily communicate and exchangemessages with each other. However, since the serial port is a welldeveloped interface, it is not necessary to spend much effort on it totune it or design a new communication protocol for it when it is used bythe operating method disclosed by the present invention. Moreover, itsprice is cheap and its cost is lower than the cost needed by theinfrared system or the bluetooth system.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention, and together with the description, serve to explain theprinciples of the invention. In the drawings,

FIG. 1 schematically shows a block diagram for the integrated interfacecircuit of a preferred embodiment according to the present invention;

FIG. 2 schematically shows a block diagram for the integrated interfacecircuit of another preferred embodiment according to the presentinvention;

FIG. 3 schematically shows a step flow chart of a preferred embodimentthat is included in the operating method for the integrated interfaceprovided by the present invention related to the operation for turningon the system first time;

FIG. 4 schematically shows a step flow chart of the process included inthe operating method for the integrated interface of a preferredembodiment according to the present invention related to thepower-saving method;

FIG. 5 schematically shows a flow chart of the steps included in theoperating method for the integrated interface of a preferred embodimentaccording to the present invention related to power charging;

FIG. 6A schematically shows a sketch map of the potential levels used bya preferred embodiment according to the present invention; and

FIG. 6B schematically shows a flow chart of the steps included in theoperating method for the integrated interface of a preferred embodimentaccording to the present invention related to the power-shortagedetermining method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically shows a block diagram for the integrated interfacecircuit of a preferred embodiment according to the present invention.The circuit for the integrated interface of the PDA (Personal DigitalAssistant) and the wireless communication system shown in FIG. 1transmits signal between the PDA 102 and the wireless communicationsystem 104 to integrate and make them into a whole. In the presentembodiment, the circuit for the integrated interface comprises aPDA-turn-on-wireless-communication-system signal line 130, aPDA-reset-wireless-communication-system signal line 132, a PDA-statesignal line 134, a wireless-communication-system-state/wake-up-PDAsignal line 136, two serial ports 110 and 112, and a power system 106.Wherein, the serial port 110 transmits the control signal and the statusdata of the wireless communication system state such as the antennaintensity and the battery capacity by using a multi-channel method, andthe serial port 112 is dedicated to transmit the digital data signal.Under normal situations, the digital data signal transmitted betweenthese two elements (usually, it is an audio signal) occupies a very longtime period on the serial port. Therefore, the present inventiontransmits the control signal and the digital data signal via separateserial ports respectively to avoid prolonging the time for transmittingthe control signal when the PDA 102 and the wireless communicationsystem 104 transmit the digital data signal to each other. Moreover, theintegrated interface does not interrupt the digital data transmissionand does not impact the real timing of the digital data due to therequirement of transmitting the control signal.

Furthermore, although it is not shown in FIG. 1 precisely, the powersystem 106 used by the present embodiment supplies power to the PDA 102and the wireless communication system 104 for their operation viarelated circuits, respectively. In addition, for the convenience ofpower management, the power system 106 of the present embodiment furtherprovides a power-shortage signal to the PDA 102 and the wirelesscommunication system 104 respectively via the signal line 120 when thepower is insufficient. Moreover, the power system 106 further provides acharging signal to the wireless communication system 104 via thecharging signal line 124. With the message provided by the chargingsignal, the wireless communication system 104 can determine themagnitude of the current and the charging circuit used for charging.

Moreover, in the present embodiment, in order to provide a further powermanagement method, the PDA 102 transmits an idle signal to the powersystem 106 via the idle signal line 122 after it is idle for a certainperiod of time, so that the power system 106 can determine the magnitudeof the power supplied to the PDA 102.

FIG. 2 schematically shows a detailed block diagram for the integratedinterface circuit of another preferred embodiment according to thepresent invention. The device 20 comprises a PDA 202, a wirelesscommunication system 252, a power system 280, and an integratedinterface composed of a serial port 22 and a serial port 24. Wherein,the PDA 202 portion comprises a processor 204, an LCD (liquid crystaldisplay) 206, a touch panel 208, an ASIC (Application SpecificIntegrated Circuit) 210, a universal I/O chip 212, an external universalI/O chip 214, an external device interface (RS232/IR) 216, a USB(Universal Serial Bus) 218, a keyboard 220, a memory 222, an audioelement 224, and an extended memory card 230. The wireless communicationsystem 225 portion comprises a processor 254, a built-in memory 256, aSIM card 258, a keyboard 260, a vibrating element 262, an LED 264, ananalog Codec (coder/decoder) 266 with an internal charging circuit 268included in it, and a wireless communication element 270 used forsending and receiving the electromagnetic wave signal. Moreover, thepower system 280 used by the present embodiment is composed of thebattery 282 and the external charging circuit 284. In addition, in theintegrated interface used to communicate between the PDA 202 and thewireless communication system 252, the serial port 22 is used totransmit a control signal, and the serial port 24 is used to transmit adigital data signal. In order to have those skilled in the related arthave better understanding of the technique contents of the presentinvention, the circuit block diagram shown in FIG. 2 is exemplifiedhereinafter to describe operating methods for the PDA and the wirelesscommunication system provided by the present invention in detail.Furthermore, in order to reduce the complexity of drawings, the signallines shown in FIG. 1, including thePDA-turn-on-wireless-communication-system signal line 130, thePDA-reset-wireless-communication-system signal line 132, the PDA-statesignal line 134, and the wireless-communication-system-state/wake-up-PDAsignal line 136 are not shown in FIG. 2. However, in order to achieveall specific functions, these signal lines are required under certaincircumstances.

Referring to both FIG. 2 and FIG. 3 simultaneously, FIG. 3 schematicallyshows a step flow chart of a preferred embodiment that is included inthe operating method for the integrated interface provided by thepresent invention and related to the operation for turning on the systemfirst time. It has to be specified that the wording of the “turning onthe system first time” used herein is switching the state of the PDA 202from turn-off state to turn-on state. For example, the turn-on operationperformed after the battery is exhausted or the PDA 202 is turned off toreplace the battery belongs to the range of “turning on the system firsttime”. Moreover, although the global system for mobile (GSM) is used asan example of the embodiment for the wireless communication system 252in the present embodiment, it does not mean that the present inventionis only suitable for the circumstance of the GSM combination, otherwireless communication systems, such as the general packet radio service(GPRS) can also be applied with the same method.

In the embodiment as shown in FIG. 3, at first, for example, a keyboardis used by the user to turn on the device 20 for the first time after itis manufactured from the factory (step S302). Since the power system 280currently used usually stores enough power for its operation, the systemwill turn on the PDA 202 first (step S304). Certainly, if the powersystem 280 does not store enough power to turn on the PDA 202, thedevice 20 cannot be turned on.

After the PDA 202 is turned on in step S304, the PDA 202 starts checkingthe status of the GSM 252 (step S306). Meanwhile, since the PDA 202 hasbeen turned on, the processor 204 recognizes the status of the GSM 252via the GSM-state/wake-up-PDA signal line 136. If the GSM 252 has beenturned on, the PDA 202 transmits the PDA-reset-GSM signal to theprocessor 254 via the PDA-reset-GSM signal line 132 to reset the GSM 252(step S312). Otherwise, if the GSM 252 is found to be turned off in stepS306, the PDA 202 transmits the PDA-turn-on-GSM signal to the processor254 via the PDA-turn-on-GSM signal line 130 to turn on the GSM 252 (stepS308). After the GSM 252 has been turned on in step S308 and afterwaiting for a predetermined period of time (step S310), the PDA 202performs the operation for resetting the GSM 252 as mentioned above(S312).

After the reset operation in step S312, the PDA 202 starts waiting foranother predetermined period of time (step S314, and this predeterminedperiod of time can be different from the waiting time in step S310mentioned above). After waiting, the PDA 202 checks the status of theGSM 252 again (step S316). If the result of checking indicates the GSM252 operates normally, the turn-on process is completed. Otherwise, ifthe result of checking indicates the GSM 252 does not operate normallyyet (step S318), the steps S314-S316 are processed repeatedly to confirmthe actual status of the GSM 252 under the circumstance that the waitingtime does not exceed the length of the predetermined period of time. Ifthe GSM 252 cannot operate normally even after waiting for thepredetermined period of time, the device 20 issues an error message tonotify the user that the GSM 252 turn on operation failed. In thepresent invention, the error message may comprise a flashing light,displaying a string on the PDA 202 or sounding a warning beep.

Although the embodiment mentioned above uses the circumstance that thedevice 20 is turned on the first time by the keyboard after it has beenmanufactured from the factory as a major foundation for description, allother methods for turning on the device that comply with the definitionof “turning on device first time” can be used with the method mentionedabove. For example, under the circumstance that the power of the powersystem 280 is completely exhausted and the device 20 has to rely onrecharging via the external charging cable for resuming its operation,after the charging cable is plugged into the device 20 and startscharging the power system 280 (step S330), the power system 280 ischarged gradually (step S332). Then, the device 20 tries to turn on thePDA 202 (step S334), and if the PDA 202 cannot be turned on yet, thedevice 20 charges the power system 280 continuously; if the power storedin the power system 280 is large enough to turn on the PDA 202, theprocess turns into the step S304 to turn on the PDA 202, andsubsequently performs the turn-on-device operation mentioned above.

Moreover, the method provided by the present embodiment is also suitablefor the general turn-on-device process after some minor modification. Asshown in FIG. 3, after the PDA 202 passes the general normal resetoperation (step S340), step S306 and its subsequent processes can becontinued to complete the turn-on-device process.

It has to be specified herein, that when a system is charging, sincethere may be some leak of electricity between those two systems (PDA 202and GSM 252), it may result in a certain unstable state, and thus theGSM 252 has to be reset after the PDA 202 is turned on to prevent thephenomenon of disorder from happening. Optionally, a switch can bedesigned in the power terminal of the GSM 252, and after the PDA 202becomes stable, the PDA 202 turns on this switch to supply power to theGSM 252. Therefore, the GSM 252 is ensured not to be turned on beforethe main controller (i.e. PDA 202) and thus will not lose its control.

FIG. 4 schematically shows a step flow chart of the process included inthe operating method for the integrated interface of a preferredembodiment according to the present invention related to thepower-saving method. The control process used for a generalwarm-turn-on-device is described herein first. Please also refer to FIG.2 at the same time, when the PDA 202 is in the standby state (stepS402), if the switch is not pressed yet, the PDA 202 keeps staying inthe standby (sleep) state, and the GSM 252 enters into the sleep state(step S404-S410). If the switch is pressed while in the standby state,the PDA 202 will wake up, and the GSM 252 is activated simultaneously(step S404-S406). Afterwards, when the switch is pressed again (stepS408), the PDA 202 will enter into the standby state, and the GSM 252enters into the sleep state. When the GSM 252 is in the sleep state, thepower system 280 does not provide the high frequency (e.g. 13 MHz) powerto the GSM 252, saving power required for switching the state of thehigh frequency element under the standby state.

Referring to both FIG. 4 and FIG. 2 again, when the GSM 252 is in thestandby state (it does not matter whether it is sleeping or not, i.e.step S412), the GSM 252 starts performing an operation for receiving atelephone signal for as long as it receives the telephone signal.Meanwhile, the GSM 252 transmits the GSM-state/wake-up-PDA signal to theprocessor 204 of the PDA 202 via the GSM-state/wake-up-PDA signal line136 to wake up the PDA 202 first. After the PDA 202 is wakened, theinput source of the audio element 224 is converted into the analog Codec266 of the GSM 252. Therefore, the electromagnetic wave received by thewireless communication element 270 can be converted into the digital (oraudio) data, and outputs it to the user via the analog Codec 266 byusing the audio element 224. Moreover, if only the GSM 252 is used andthere is no action applied to the PDA 202 for a certain period of time,the PDA 202 enters into the sleep state from the wake-up state to reducethe electricity wear.

In addition, there is still another method for saving the electricitywear. That is, as shown in FIG. 1, when the PDA 102 stays in the idlestate, the PDA 102 provides an idle signal to the power system 106 viathe idle signal line 122. The power system 106 changes to use a newmethod that saves more electricity to output power after it receivesthis idle signal, so as to save some electricity wear.

FIG. 5 schematically shows a flow chart of the steps included in apreferred embodiment according to the present invention and related tothe power charging. In order to have a better understanding, please alsorefer to FIG. 2 at the same time. When the charging cable is pluggedinto the power system 280 and starts charging (step S502), the externalcharging circuit 284 inside the power system 280 starts charging to thebattery 282 with a small-current charging method (step S504). Meanwhile,the power system 280 sends a charging signal to the GSM 252 to notify itthat it is in the charging state now. After the small-current chargingis started, the device 20 starts trying to turn on the GSM 252. If theGSM 252 cannot be turned on, the small-current charging is continuouslyperformed; otherwise, if the GSM 252 is turned on successfully, theprocess enters into next step's charging process (step S506). After theGSM 252 is turned on successfully, the internal charging circuit 268inside the GSM 252 starts to operate, and with this, it performs fasterspeed's charging to the battery 282. For example, when the potential ofthe battery 282 is lower than 3.6 V, the internal charging circuit 268uses 600 mA as the current value for the first segment's charging (stepS508, S510). When the potential of the battery 282 is in between 3.6 Vand 4.2 V, the internal charging circuit 268 uses 900 mA as the currentvalue for the second segment's charging (step S512, S514). After thepotential of the battery 282 achieves 4.2 V, the internal chargingcircuit 268 changes to use the constant-voltage charging method tocharge the battery 282 (step S516), so that the battery 282 is notdamaged due to over-charging.

FIGS. 6A and 6B schematically shows a sketch map of the potential levelsand a step flow chart used by a preferred embodiment according to thepresent invention, respectively. In FIG. 6A, the present inventiondivides the battery potential into five different levels, they are: fullbattery 60, low battery (C) 62, insufficient battery (A) 64,insufficient battery (B) 66, and complete discharge 68, respectively. Inan embodiment of the present invention, the potential represented bythese levels is: full battery 60 indicates the current battery potentialis above 3.8 V, low battery (C) 62 indicates the current batterypotential is in 3.8V˜3.6 V, insufficient battery (A) 64 indicates thecurrent battery potential is in 3.6V˜3.5 V, insufficient battery (B) 66indicates the current battery potential is in 3.5V˜3.2 V, and completedischarge indicates the current battery potential is below 3.2V,respectively. Certainly, the dividing standard for the battery potentiallevels does not have to match the present embodiment, those skilled inthe related art can appropriately adjust the dividing standard, thefigures listed above are only exemplified herein and do not serve as thenecessary limitation condition for the present invention.

The power-shortage determining method provided by the present inventionis further described in detail hereinafter. In order to have a betterunderstanding and facilitate the explanation, please refer to both FIG.6A and FIG. 6B at the same time. In FIG. 6B, it is assumed that thebattery 282 is in the full battery 60 state at first (step S602),meanwhile all operations for the device 20 operate normally. After thedevice 20 continuously uses power and makes the potential of the battery282 fall in the range of the lowest battery (C) 62 (step S604), thepower system 280 determines whether to issue the battery-shortage signalor not (step S606).

The standard used in step 606 for determining whether to issue thebattery-shortage signal or not is further described hereinafter. It isassumed that the battery 282 is in low battery (C) 62, and the devices20 are heavy loaded, such as the state when the PDA 202 is using theaudio element 224 or the GSM 252 is using telephone. Since it uses morecurrent, the potential of the battery 282 easily falls into the range ofinsufficient battery (B) 66 immediately. Therefore, after the potentialof the battery 282 enters into the range of the low battery (C) 62, ifthe device 20 turns to heavy loading from light loading (e.g. sleepmode) suddenly, the power system 280 issues the battery-shortage signalwhen the potential of the battery 282 is lower than the insufficientbattery (B) 66. If the device 20 keeps staying in the light loading, thepower system 280 issues the battery-shortage signal when the potentialof the battery 282 is lower than the insufficient battery (A) 64. Inother words, the criteria for generating the battery-shortage signal canbe adjusted automatically depending on conditions.

If after step S606, it is determined not to issue the battery-shortagesignal, the battery 282 stays in the low battery state and does notenter into the insufficient battery state; if it is determined to issuethe battery-shortage signal, the power system 280 provides thebattery-shortage signal to the PDA 202 and GSM 252, respectively. Thisindicates the battery 282 has entered into the level of insufficientbattery already (step S608). To be noted, the current battery potentialmay fall into the level of either insufficient battery (A) 64 orinsufficient battery (B) 66. Once the power system 280 issues thebattery-shortage signal, the battery-shortage signal is not releaseduntil the potential of the battery 282 is higher than that of the lowbattery (C) 62. If the user continuously uses it, after the potential ofthe battery 282 is lower than insufficient battery (B) 66, the powersystem 280 enters into the level of complete discharge and is notallowed to execute any operation.

To be specified herein, since the sudden fall of the battery voltage iscommonly generated when it is changed from light loading to heavyloading, the electrical energy actually stored in the battery may stillbe big enough to support the power that is required for normaloperation. Therefore, the battery-shortage determining method providedby the present invention can avoid the condition of abnormal deviceturn-on and turn-off resulting from the system not recognizing thebattery-shortage due to the light loading to heavy loading change byflexibly adjusting the criteria for determining battery-shortage.

In summary, the advantages of the present invention are describedhereinafter. The present invention transmits control signals and digitaldata respectively by using two serial ports, thus to simplify thecommunication protocol generally considered and used to transmit controlsignals and digital data simultaneously by using a single serial port.Moreover, not only is the hardware cost much less than the cost neededfor infrared system or bluetooth system, but also provides an efficientmethod for managing power, so that power waste can be eliminated.

Although the invention has been described with reference to a particularembodiment thereof, it will be apparent to one of the ordinary skill inthe art that modifications to the described embodiment may be madewithout departing from the spirit of the invention. Accordingly, thescope of the invention will be defined by the attached claims not by theabove detailed description.

1. A circuit for an integrated interface of a PDA and a wirelesscommunication system, suitable for integrating the PDA and the wirelesscommunication system, the circuit comprising: a first serial port,having two terminals, wherein one of the two terminals is electricallyconnected to the PDA, another one of the two terminals is electricallyconnected to the wireless communication system, and the first serialport is used to bi-directionally transmit a control signal between thePDA and the wireless communication system; and a second serial port,having two terminals, wherein one of the two terminals is electricallyconnected to the PDA, another one of the two terminals is electricallyconnected to the wireless communication system, and the second serialport is used to bi-directionally transmit audio data between the PDA andthe wireless communication system.
 2. The circuit of claim 1, furthercomprising a power system, the power system providing a power to the PDAand the wireless communication system respectively, and determining themagnitude of the power provided to the PDA according to an idle signaltransmitted from the PDA.
 3. The circuit of claim 2, wherein the powersystem provides a power-shortage signal to the PDA and the wirelesscommunication system respectively when the power is insufficient.
 4. Thecircuit of claim 1, wherein the first serial port is further used totransmit status data of the wireless communication system.
 5. Thecircuit of claim 4, wherein the status data includes an antennaintensity.
 6. The circuit of claim 1, wherein the audio data is digitaldata.
 7. The circuit of claim 6, wherein the wireless communicationsystem includes a wireless communication element used for receiving anelectromagnetic wave signal, and the electromagnetic wave signal isconverted into the digital data.
 8. The circuit of claim 7, wherein thePDA includes an audio element for receiving the digital data through thesecond serial port.
 9. An operating method for an integrated interfaceof a PDA and a wireless communication system, suitable for integratingthe PDA and the wireless communication system, the operating methodcomprising: using a first serial port to bi-directionally transmit acontrol signal between the PDA and the wireless communication system;and using a second serial port to bi-directionally transmit audio databetween the PDA and the wireless communication system.
 10. The method ofclaim 9, wherein the audio data is digital data.
 11. The method of claim10, further comprising: receiving an electromagnetic wave signal by awireless communication element; and converting the electromagnetic wavesignal into the digital data.
 12. An operating method for an integratedinterface of a PDA and a wireless communication system, suitable forintegrating the PDA and the wireless communication system, the operatingmethod comprising: using a first serial port to transmit a controlsignal between the PDA and the wireless communication system; using asecond serial port to transmit audio data between the PDA and thewireless communication system; and when the PDA is turned on, performingthe following steps: turning on the PDA; and turning on the wirelesscommunication system by the PDA.
 13. The operating method of claim 12,further comprising: resetting the wireless communication system afterturning on the wireless communication system.
 14. The operating methodof claim 13, further comprising: after resetting the wirelesscommunication system and waiting for a first predetermined period oftime, checking a status of the wireless communication system; if thestatus of the wireless communication system is normal, theturn-on-device is completed; and if the status of the wirelesscommunication system is abnormal, displaying an error message toindicate that turning on the wireless communication system is infailure.
 15. The operating method of claim 12, wherein the step ofturning on the wireless communication system by the PDA, furthercomprising: transmitting a PDA-turn-on-wireless-communication-systemsignal from the PDA to the wireless communication system to turn on thewireless communication system.
 16. A circuit for an integrated interfaceof a PDA and a wireless communication system, suitable for integratingthe PDA and the wireless communication system, the circuit comprising: afirst serial port, having two terminals, wherein one of the twoterminals is electrically connected to the PDA, another one of the twoterminals is electrically connected to the wireless communicationsystem, and the first serial port is used to transmit status data of thewireless communication system between the PDA and the wirelesscommunication system; and a second serial port, having two terminals,wherein one of the two terminals is electrically connected to the PDA,another one of the two terminals is electrically connected to thewireless communication system, and the second serial port is used totransmit audio data between the PDA and the wireless communicationsystem.
 17. The circuit of claim 16, wherein the status data includesone of an antenna intensity and a battery capacity.
 18. The circuit ofclaim 16, wherein the audio data is digital data.
 19. The circuit ofclaim 18, wherein the wireless communication system includes a wirelesscommunication element used for receiving an electromagnetic wave signal,and the electromagnetic wave signal is converted into the digital data.20. The circuit of claim 19, wherein the PDA includes an audio elementfor receiving the digital data through the second serial port.
 21. Thecircuit of claim 16, wherein the status data includes an antennaintensity.